The invention concerns a lock cylinder and, in particular, a lock cylinder having tumblers mechanically lockable by a key which permits the transmission of coding information between an electronic control circuit of the key and an electronic control circuit of the lock cylinder.
European Patent Document EP-A-0,324,096 discloses a profile lock cylinder comprising a profile housing and a cylinder core rotatably seated in a bore of the profile housing, having a keyway extending in the direction of the axis of the cylinder for insertion of a flat key. The key controls not only mechanical tumblers of the lock cylinder but includes an electronic control circuit in its bow section. Inductively via a key-side coupling coil, the control circuit transmits coding data to a coupling coil on the profile housing. An additional electronic control circuit connected to the coupling coil of the lock cylinder evaluates the transmitted coding data and, upon agreement between key-side and lock-cylinder-side coding data, generates a control signal corresponding to the lock status. In addition to the tumblers mechanically actuable by the key, the lock cylinder comprises an electromagnetic locking means which also blocks the cylinder core relative to the profile housing, and which can be unlocked by the control signal.
The coupling coil of the lock cylinder disclosed in European Patent Document EP-A-0,324,096 is disposed in a mounting of synthetic material which is held at one front end of the profile housing by means of integral locking members. The mounting of synthetic material projects beyond the front face of the cylinder core, to bring the coupling coil nearer to the coupling coil disposed in the bow on the key side. In a door-mounted lock, for example, the mounting of synthetic material thus projects a few millimeters beyond the front of a door plate, resulting in a risk of unintentional damage and unauthorized manipulations.
Usually, the magnetic fields of the coupling coils are comparatively small, and the signals produced by the lock-cylinder-side coupling coil are also comparatively small. This makes it necessary to place the electronic control circuit as close as possible to the coupling coils, to reduce signal losses and interference. In known electronic lock cylinders responding to coding information of the key, the electronic control circuit or at least some of its components may be accommodated within the housing of the lock cylinder. However, assembly of this type of lock cylinder is difficult, as electronic and mechanical components have to be assembled simultaneously.